Microwave Fibre Orientation Sensor

A new sensor based on a microwave resonator for measuring the fibre orientation in sheets was developed. The device is non-contacting and is suitable for measurements of moving web in paper and board machines. It can also be applied to measure the molecular orientation of plastic films. With this novel method, the fibre orientation can be measured without rotating the sample and the sensor with respect to each other The measurement results of the device were compared to the results obtained with ultrasonic tensile stiffness orientation on paper samples (TSO). TSO gave identical orientation angles but the orientation ratios were different in some samples. This is because TSO is also sensitive to strains in fibre, whereas the microwave method reflects the true geometric fibre orientation. The uncertainty of the orientation angle measurement with the microwave device is less than 0.4 degrees.